So this isn't doing what you think it's doing. When the players leave a game, they are leaving the DM's power and authority and going elsewhere. They are not removing or diminishing his power or authority over his game.
There is no "his game". It doesn't exist. There is only "their game". A GM with no players
has no game. They can have plans for a campaign or an adventure, but unless they are ignoring all player agency, players leaving or changing will mean the game will not take the same route and end up the same place it would have if they stayed, showing that the game belongs to all of them.
Lord of the Rings would be very different story if Samwise walked halfway through.
Power isn't a point source - it's a description between things. Walk, and the GM has no power over you. I've even walked with all the players away from a game before and we just started a new game.
That DM can go out and get more players and continue that game.
No, the GM can (potentially) go out and get more players and create a new game that is based on what they have done before. If they have retained some players there can even be more continuity, like a show where a lead actor or director leaves and something with that same name continues, but it doesn't have the same chemistry or the same energy and needs to rediscover itself.
And again, your statement seems to assume that players are cogs - you can replace them and they all bring the same thing to the table. So there never a penalty to losing them. That's a very senior management view you have there, one that isn't held up in the real world.
Players don't grant the DM authority. The game does.
Please, exercise that authority given by the game over me.
You can't, because I don't grant you that authority over me by accepting you as a GM. See, the rules grant you no authority, only I can grant it. And take it away.
Tell me how the rules have
FORCED a player to accept authority when the player wants to leave the game. Again, your thesis is that the rules grant this authority and not the players, and by your thesis you can use that power even when the players do not want you to. Please, tell me how.
There is literally no way the game grants any authority not granted by the player. There is no mechanism to make a player accept something if they do not wish to enough to leave the game.
The DM can cede some of that authority to the players, though.
The social contract is really the only limiter. Groups gather to have fun, so the DM abusing his authority and removing or diminishing that fun is a violation of the social contract. The vast majority of DMs choose to play within the confines of the social contract, so they do not use their authority in abusive ways.
This again is due to the social contract. There's nothing in the rules that prevents a DM from abusing his authority and engaging in such things.
I'm not really sure where you are going with this, because it's a pointless distinction. Regardless if it's because a DM is abusing their power, are just a bad DM, are a great DM but not a good match for how the player wants to play, if the DM claims the rules give them authority but also claim they can change the rules as they want, all of it doesn't matter. If a GM is net decreasing fun the players can take away the power they have granted the DM over themselves by walking.